1. Field of the Invention
The present invention relates to telemetry systems in general and more specifically to a system for instrumenting a ballistic projectile with a miniaturized sensor(s) and a telemetry system for testing and evaluation.
2. Discussion of Related Art
The in-flight measurement of artillery projectile flight dynamics (acceleration, pitch, yaw, spin and derivative thereof) or diagnostics of on-board devices (fuzing, warhead, etc) has been routinely accomplished at the Amy Research Laboratory. In most applications, commercial telemetry subsystems such as voltage controlled oscillators, transmitters, antennae, sensors, etc., could be located in either the nose, ogive, body, base or in some cases, all sections of the projectile. Typical volumes for these systems could range from 9 cubic inches to 27 cubic inches depending on the application.
Another example of prior art is as such, a test engineer wants to measure spin and yaw on a KE projectile. Kinetic energy projectiles, such as the one featured in FIG. 1, usually consist of a long slender rod, a pointed windshield, and a small set of fins. There isn""t much room to install an instrumentation pack of any sort. The current state of the art process involves setting up several large placards in the flight path of the KE projectile. These placards are placed at precise distances from the muzzle of the gun tube. The KE projectile passes through these placards leaving fin-shaped holes. The engineer then has to digitize the shapes of the holes into a computer, where an algorithm determines the spin rate and attitude dynamics. This is usually accomplished from several minutes to several hours after the test has been performed.
A separate example of measuring spin was an experiment that Motorola performed at the Ballistic Research Laboratory. A spin stabilized, 105 millimeter KE training round was instrumented with a small device. The device incorporated a small power supply, transmitter and antenna. The device transmitted a pilot tone while the projectile was in free flight. The transmission used the C-band frequency, which is not compatible with military testing specifications. No sensor was incorporated into this device.
The current state of the art process of measuring projectile base pressure involves drilling small holes into the breech of a cannon tube and installing pressure gages. The gages measure the pressure event and a digital computer algorithm extrapolates the data to provide an estimate of the actual pressure and accelerations experienced by the projectile while travelling through the cannon tube. The procedure is very quick; however, the base pressure and the acceleration are still numerically derived. Future gun systems will be more complicated in design and difficult to instrument in the fashion previously mentioned.
Accordingly, it is an object of the present invention to provide a hardened subminiature telemetry and sensor system for a ballistic projectile.
Ballistic projectiles include kinetic energy (KE) projectiles, which are launched from a tank cannon, and artillery projectiles which are launched from artillery cannon. These types of ballistic projectiles are un-guided There is a need to provide a continuous measurement of the environments of both in-bore and free-flight events. The environments are severe since KE projectiles are launched from tank gun cannons at accelerations in excess of 100,000 g""s. Artillery projectiles are launched with less acceleration, however, the projectiles exit the cannon with spin rates of about 18,000 revolutions per minute. The geometry of the KE projectile is a long, solid rod, with a thin pointed windshield and a small set of fins for stanbilization. With the exception of the tracer well cavity, there is no space on a KE projectile for an instrumentation package. Modifications to the projectile can create adverse effects to the trajectory and are therefore not allowed. Through the use of mini ed sensor(s), batteries, acceleration switches, signal conditioning electronics, transmitter and antenna, the present invention will provide simultaneous in-flight measurements of both the in-bore and free-flight environment. As soon as the projectile exits the cannon tube and is experiencing a free-flight trajectory, the present invention will telemeter the data to a nearby ground station. The sensors will measure projectile spin history, axial and transverse accelerations, pitch and yaw angles and rates, temperature, base pressure, or a combination thereof. This invention will improve the testing and evaluation of a projectile The invention is rugged, being capable of surviving temperatures in excess of 3500 degrees K, accelerations of 100,000 g""s and spin rates in excess of 1,000 Hz. The invention is also extremely compact, taking up to 0.5-1.0 cubic inches of volume, thus making it much easier to instrument any projectile.
Ammunition testers could thread this invention into the existing tracer well of a KE projectile, as seen in FIG. 2, and measure the actual environment of the projectile continuously and more accurately. The tracer is a gas/flame generator which serves two purposes: first to help the gunner to track the projectile while in flight, and secondly, to reduce any base drag on the projectile. If a manufacturer need to test a specific lot of KE projectiles, the installation can be easily incorporated in the assembly. Instead of a tracer, the manufacturer can install the invention, which used the same threads as the tracer. The intent of the invention is not about the individual technologies or the miniaturized electronics, but the incorporation of the technologies into one device.